Twelve new alkaloids have been obtained from the root bark, trunk bark, and leaves of Aspidosperma marcgravianum: 16-epi isositsirikine 3S,4S N-oxide (36), 3,4,5,6 tetradehydro-18,19 dihydrocorynantheol (37), 2-ethyl-3[2-(3-acetylpiperidino) ethyl] indole (38), 18-oxohaplocidine (39), l6(S)isositsinkine N-oxide (40, 18, 19-dihydroantirhine (41), isogeissoschizol (42), 10-methoxy-isogeissoschizol (43), isoantirhine (44) 17,4’,5’,6’ tetra-hydro-17(R) usambarensine N-oxide (45), Nb-carbomethoxy-17,4’,5’,6’ tetrahydro-17(R)usambarensine (46), Nb-carboethoxy-17,4’,5’,6× tetrahydro-17(R)usambarensine (47). Thirty-four known alkaloids were also isolated: 16 of them have been obtained for the first time from the genus Aspidosperma. © 1983, American Chemical Society. All rights reserved.